Softswitch technical standards and Evolution Process

As the core technology of the Next Generation Network, the development of Softswitch technology has been very mature so far. When data services gradually replace voice services as the main source of revenue, the evolution to a data-based group network is inevitable. As voice is still an important service, the next generation network must provide QoS Assurance according to different service requirements. Therefore, the main driving force behind the evolution of network technology to the NGN network is formed.

As the core technology of the Next Generation Network, Softswitch is based on call and bearer separation. The starting point of the Softswitch technology was to gradually transition the existing circuit switching network to the IP network and replace the traditional circuit switching network. At the same time, it provides more services for IP phones, so that the IP network can obtain the same services as the traditional circuit switching network.

Overview of Softswitch Technology

The Softswitch technology of the fixed network NGN is now basically developed based on two technical routes: one is to transplant services in the traditional circuit switching field to the group bearer network for implementation. The other is a brand new all-IP-based multimedia business system. For the first route, traditional telecom services are transferred from dedicated TDM to a unified shared IP/ATM multi-service transmission network, in addition, the network layer service transmission is segmented by the Access Gateway while the user access mode remains unchanged. The original circuit switching network device is divided into two parts: the control plane SoftSwitch and the bearer Plane Media Gateway, however, the end users of PSTN/ISDN/PLMN cannot feel the changes in their business characteristics and access methods.

For the brand-new all-IP-based multimedia service system, the real end-to-end IP service features are achieved, and new real-time multimedia applications including voice are introduced. Users access the softswitch technical network through SIP/H.323 grouping terminal. The network architecture and service provision methods (such as SIP) are completely different from the traditional circuit switching network. UMTS mobile's 3GPP R4 and R5 stages correspond to the two technical routes of the above-mentioned Softswitch technology development.

Next-generation core network circuit domain of the mobile network

1.3GPP circuit domain core network

The Application of Softswitch technology in 3GPP core network mainly involves two aspects: Circuit domain and IMS subdomain. In R4 of 3GPP, the core network of the circuit domain introduces the network structure of control and bearer separation. In the circuit domain of the core network of the mobile exchange server, different transmission layers, such as IP, ATM, or TDM, can be supported independently. The circuit domain core network consists of MSC Server, GMSC Server, and MGW.

(1) The Mobile Exchange Server (GMSC Server and MSC Server) is the core device for the evolution of the circuit domain core network to the packet exchange mode in the UMTS mobile communication system. It is independent of the underlying bearer protocol, it provides Call Control, Media Gateway Access Control, mobility management, resource allocation, protocol processing, routing, authentication, billing, and other functions, it also provides users with the services that the core network of the circuit domain can provide in the 3GPP R4 phase, as well as various third-party services in combination with smart SCP.

(2) Media Gateway (MGW) is a media format required to convert media in one network to another. The media gateway can be switched between the bearer channel of the Circuit Switching Network and the media stream of the sub-network. It can process audio and video, perform full-duplex media translation, and demonstrate video/audio messages, other IVR functions can also be used for Multimedia conferences. GMSC Server and MSC Server Control MGW through Mc interface. GMSC Server and MSC Server are connected through the Nc Interface. Mgws are connected through Nb interfaces. Where:

(1) Mc interface: the interface between MSC Server and MGW. The main function is media control. Use the H.248-based call bearer control protocol. The Protocol includes ipvpp29. 232, H.248, MeGaCo, and Q.1950.

(2) Nc Interface: it is the interface between MSC Server and (G) MSC Server. It mainly solves the Call Control of mobile ISUP by means of control and bearer separation. Call Control Protocols separated from the bearer are used, such as BICC and SIP-T.

(3) Nb Protocol: interfaces between mgws. The main function is to use an ATM or IP address to carry the business of the circuit domain, including voice and electrical domain data. The bearer protocol for the 3GPP circuit domain is used in group switching mode. The main content of the Nb interface includes ipvpp29. 415.